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Nov. 9, 2010 -- Postmenopausal women who use hormone replacement therapy face a 29% increased risk of ovarian cancer, according to a study.

Researchers at the Cancer Epidemiology Unit at the University of Oxford in England analyzed data from the European Prospective Investigation Into Cancer and Nutrition to evaluate the relationship between hormone therapy use during the postmenopausal years and ovarian cancer risk.

Hormone Therapy and Risk for Ovarian Cancer

Investigators led by Konstantinos Tsilidis, PhD, looked at data on 126,920 postmenopausal women who did not have a history of cancer and who had not had their ovaries removed. During nine years of follow-up, there were 424 cases of ovarian cancer diagnosed.

The women were also asked about their height and weight, whether they smoked, use of oral contraceptives, number of pregnancies, and what age they started menstruating.

After accounting for other factors, the research team found that:

45% of the group had used hormone therapy at some point.

30% were current users of hormone therapy when the study started.

69% of the group that used hormone therapy took an estrogen-progestin combination, 18% used estrogen-only hormone therapy, 3% used tibolone, and 2% used other preparations of hormone therapy; 8% had missing information on type of hormone use.

Current use of any hormone therapy was significantly associated with a 29% increased risk of ovarian cancer compared to women who had never used hormone therapy.

Current use of estrogen-only therapy was associated with a 63% increased risk of ovarian cancer.

Current use of estrogen-progestin combination therapy was not significantly associated with risk.

Women who had ever used some form of hormone therapy for five or more years had a 45% higher risk for ovarian cancer compared with women who had never used hormone therapy.

The findings were presented at the Ninth Annual American Association for Cancer Research Frontiers in Cancer Prevention Research Conference held in Philadelphia.

“This study is consistent with previous recommendations that say if women are going to take hormones they should only take them in the short term,” Tsilidis says in a prepared statement.

Hormone Therapy and Breast Cancer

Previous research has shown an association between hormone replacement therapy and an increased risk for breast cancer. A study published last month in The Journal of the American Medical Association found that postmenopausal women who take a combination of estrogen and progestin therapy face a greater risk for developing a more advanced form of breast cancer and an increased risk for dying from the disease. The findings were based on the ongoing Women’s Health Initiative, a major research program launched in 1991 by the National Institutes of Health.

In the United States, ovarian cancer is the fifth leading cause of cancer death. According to 2006 data from the CDC, 19,994 women in the U.S. were diagnosed with ovarian cancer and 14,857 women died from the disease.